CVE-2026-81509

6.1 MEDIUM 0.3% exploit odds Fix listed Auth & access Web app

What it is

nforwardauth is a forward auth service that allows the use of a single authentication middleware for multiple sites. Versions prior to 1.5.1 accept an unvalidated `r` query parameter on the `/login` endpoint and use them as the post-authentication redirect destination. An unauthenticated attacker can create a legitimate `nforwardauth` login URL that redirects a victim to an attacker-controlled website after the victim successfully authenticates. This issue may facilitate phishing and other social-engineering attacks by abusing the trust associated with the legitimate authentication domain. This vulnerability does not provide an unauthenticated ForwardAuth bypass. Version 1.5.1 contains a patch.

At a glance

Exploitability: Can be exploited over the network without logging in, but needs a user to act. Limited direct impact.
Exploit odds: 0.3% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-08-26 20:58 UTC ReservedThe CVE id was reserved by its CNA
2026-10-26 18:18 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-10-26 20:18 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.3% in the next 30 days (EPSS).
Severity: 6.1 MEDIUM (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-10-26 18:18 UTC
Last modified: 2026-10-26 20:18 UTC
Exploit probability: 0.3% · EPSS, next 30 days
Weakness: CWE-601
Record status: Deferred

Attack profile CVSS 3.1 · 6.1

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: Required
Scope: Changed
Confidentiality: Low
Integrity: Low
Availability: None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Is it in your code?

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Fix and advisories

References

NVD record · CVE.org record